(1) Field of the Invention
The invention relates to an automatic document feeder (ADF), and more particularly to the ADF with a releasing device for removing jammed papers to recover its normal operation.
(2) Description of the Prior Art
In the 90's, a scanner was a rather expensive computer peripheral device. For its complex operating procedure, the scanner was mainly used by professional digital image operation users. However, with an well development of the imaging technologies in the recent years, lots of low-cost and user friendly scanners have been crowded into the market and the scanners have become an indispensable part for personal users or small-sized offices.
Scanners at present are classified into feeder type and flatbed type. The flatbed type scanner has a similar design with respect to a small-sized copier by placing papers, books, or other documents to be scanned on a glass plate. Characterized with small size and low cost, the flatbed type scanner is more popular among self-employers. In addition, with the progress of scanning technologies, the scanning of three-dimensional objects has become feasible for the flatbed-type scanners.
In contrast with the flatbed-type scanners, feeder-type scanners are mainly used to satisfy the demand in large amount documents circumstance. A major advantage of feeder-type scanners is the so-called multi-page continuously scanning function, which leads to a relatively high scanning speed. However, also characterized by the multi-page scanning design, feeder-type scanners cannot scan stapled documents, photographs, or three-dimensional objects.
In order to increase the scanning speed of the flatbed-type scanners, an automatic document feeder (ADF) is reinvented to assemble on the flatbed-type scanner for proceeding multi-page continuously scanning to meet the need of large amount paper sheets. FIG. 1A shows a cross section view of a traditional ADF 100 with a feeding path 110 arranged therein. FIG. 1B is an enlarged view depicting the portion shown in FIG. 1A encircled by central line and indicating the feeding path 110 by the arrow. As shown, the traditional ADF 100 has a feeding path 110, a paper cartridge 120, a feeding roller 130, a relay roller set 140, and an exit roller set 150. The front edge 120a of the cartridge is aligned with the inlet 110a of the feeding path 110. The feeding roller 130 is located by the inlet 110a to carry a paper sheet along the feeding path 110 to a reading position 160 to be scanned, copied, or the like. The relay roller set 140, which is located in the middle of the feeding path 110, includes an active roller 142 and an idle roller 144 leaning against each other. The active roller 142 and the idle roller 144 are located on the opposite sides of the feeding path 110 respectively to clip and feed the paper sheet to the reading position 160. The exit roller set 150, which is located by the outlet 110b of the feeding path 110, includes an active roller 152 and an idle roller 154 located on the opposite sides of the feeding path 110 and leaning against each other for carrying the scanned paper sheet away from the reading position 160.
It is noted that the paper sheet inside the ADF is transmitted by the friction force from the rollers. A too much friction force may damage the paper sheet or even induce paper jam. That is, as shown in FIG. 1B, along the feeding path 110, the positions near the relay roller set 140 and the exit roller set 150 are most likely to have paper jam occurred because the friction force reaches a maximum.
When paper jam occurs, quickly removal of the jammed paper sheet is required for recovering the normal operation of the ADF. FIG. 2 shows a typical method for removing the jammed paper sheet in the traditional ADF 100 of FIG. 1. If the paper sheet is jammed in the exit roller set 150, the user has to pull the jammed paper sheet through the outlet 110b of the feeding path 110 along the direction shown by arrow to recover the normal operation of the ADF 100. If the paper sheet is jammed in the relay roller set 140, the user has to open a cover 170 to expose the relay roller set 140 and then pull the jammed paper sheet upward along the direction shown by the arrow to recover the normal operation of the ADF 100.
Both the foregoing situations of removing jammed paper sheet involve applying force to pull the jammed paper sheet from the leaned rollers, thus, the following problems may occur.
Firstly, when pulling the jammed paper sheet out the ADF, some damage or even tearing event on the paper sheet is unavoidable. If there is no backup or the document is highly important, such removal method may probably lead to an unrecoverable mistake.
Secondly, improper pulling force applied on the ADF may probably damage the ADF and shorten the expecting life of the ADF.
Thirdly, as a paper sheet of highly important is severely jammed in the ADF, the only way is to send the ADF back to the dealer for repairing and removing the jammed paper sheet. Obviously, this may lead to a considerable maintenance expense and a significant time cost.